In one aspect, this invention relates to a process for preparing telechelic compounds by metathesis of high molecular weight olefin copolymers containing ethylenic unsaturation. In another aspect, this invention relates to telechelic compounds prepared by methathesis. The resulting products are ideally suited for use in production of polyurethanes, polyesters, epoxies, and other condensation polymer compositions, as reactive diluents for high solid content coating formulations, in cosmetic formulations, and in other applications due to their desirable balance of viscosity and functionality.
Telechelic compounds bear reactive terminal functional groups. Through these reactive end groups and functionalized derivatives thereof, a vast number of macromolecular materials can be prepared. Telechelic compounds have found application in the synthesis of block copolymers, star polymers, crosslinked polymer networks, and ionic polymer networks. Low molecular weight liquid telechelic polymers have been successfully used in reaction injection molding and in the formation of ABA triblock and multiblock copolymers.
Numerous olefin metathesis processes are previously known in the art. In general, olefin metathesis involves catalytic cleavage of one or more olefins at a point of unsaturation and recombination of the resulting cleavage products to form different olefin containing reaction products. Often, low molecular weight olefins and cyclic olefins, such as ethylene, cyclopentene or cyclooctene are employed as reagents in the foregoing reaction mixtures in order to provide low viscosity reaction mixtures, well defined reaction products, reduced molecular weight products, and/or mixtures suitable for reaction injection molding (RIM) compositions and elastomers. Metathesis of two or more different olefins is referred to as a “cross-metathesis”. Examples of the foregoing processes are disclosed in U.S. Pat. Nos. 5,731,383, 4,994,535, 4,049,616, 3,891,816, 3,692,872, and elsewhere.
Preparation of linear polyethylene and poly(ethylidene-norbornene)/polycyclopentene diblock copolymers by ring opening metathesis of polycyclopentene or sequential polymerization of mixtures of ethylidenenorbornene and polycyclopentene was disclosed in Macromol., 33(25), 9215-9221 (2000). In Macromol., 33, 1494-1496 (2000), solid polymers were depolymerized by surface contact with a metathesis catalyst.
Functionalized polymers obtained through use of an appropriately functionalized cyclic or acyclic olefin chain transfer agent containing hydroxyl, ester, borane or reactive silyl functionality or through subsequent process steps may be employed to introduce the desired functionality into the polymers. Examples of such processes are disclosed by U.S. Pat. Nos. 6,867,274, 6,410,110, 5,603,985, 5,559,190, 5,446,102, 4,049,616, and other references.
In U.S. Pat. Nos. 3,692,872, 3,891,816 and 4,010,224 graft and block copolymers and interpolymers were prepared by metathesis of two polymers containing olefinic unsaturation, such as polybutadiene or polyisoprene. Monomers such as cyclooctene or dimers, such as cyclooctadiene-cyclopentadiene dimer, could be included in the polymerization as well. Similar processes involving the cross-metathesis of polybutadiene with polycyclooctene or polycyclododecene as well as grafting of EPDM polymers via metathesis were disclosed in DE 2,131,355 and DE 2,242,794. A summary of the work appeared in J. Mol. Catal., 15, 3-19 (1982).
In Macromol. Chem. Rapid Commun. 14, 323-327 (1993) and Macromol., 36, 9675-9677 (2003) the ethenolysis of partially hydrogenated polybutadiene and of propylene/1,3-butadiene copolymers were disclosed. The former process yielded α,ω-divinyl polyethylene oligomers containing a high internal ethylenic unsaturation (approximately one internal C═C bond in every two polymer chains). Studies of the latter product showed increased melting points for the metathesized reaction product presumably due to closer packing of the crystalline polymer segments.
Telechelic polymers with crosslinkable end groups such as hydroxy, acrylate or epoxide groups are useful for the preparation of interpenetrating polymer networks, crosslinked polymeric materials, coatings, encapsulating compositions, and for the immobilization of biomaterials. In U.S. Pat. No. 7,022,789, the depolymerization of copolymers prepared by ring opening metathesis polymerization (ROMP) of cyclooctadiene (COD) with either cis-4,7-dihydro-1,3-dioxepan or cis-4,7-dihydro-2-phenyl-1,3-dioxepan using ruthenium complexes, resulted in a polymer bearing both poly(butadiene) and acetal units along the backbone. Subsequent acid hydrolysis of these acetal units resulted in the formation of hydroxytelechelic poly(butadiene) (HTPBD) oligomers. Also disclosed was the direct preparation of telechelic polymers having crosslinkable end groups by reacting a functionalized chain transfer agent with a cycloalkene in the presence of certain ruthenium or osmium ROMP catalysts. Similar processes using difunctional olefins such as 2-butenedicarboxylic acid diesters under ROMP or metathesis degradation conditions were disclosed in German Democratic Republic patents DD 146,052 and DD 146,053, respectively. Suitable polymers for the latter process included, “1,4-cis-polybutadiene, and other copolymers as ABS rubber or SB rubber”. According to U.S. Pat. No. 7,022,789, the products were polydisperse rubbers indicating the presence of cross-linking and containing undesirable quantities of vinyl groups.
The previously discussed processes utilized polybutadiene or similar polymers prepared by free radical techniques which possess undesirably high quantities of pendant vinyl groups (instead of terminal or internal unsaturation) due to uncontrolled 1,2-addition of the conjugated diene. This results in undesirably high levels of pendant vinyl functionality in the metathesis products and higher average functionality (greater than 2.0) unless extensive hydrogenation of the polymer is employed to first reduce the level of such pendant unsaturation. Polymer hydrogenation, however, is expensive and can result in loss of terminal unsaturation as well. Moreover, polybutadiene is known to be subject to rapid metathetical degradation and ring formation under metathesis conditions, resulting in formation of low molecular weight by-products of little commercial value.
It would be desirable if there were provided a process for the metathesis of unsaturated polymers that is specifically adapted for the formation of differentiated, commercially valuable telechelic products having desirable properties, especially low internal unsaturation for use in preparing functionalized derivatives such as polyols. It would further be desirable if the resulting products were suitable for use in preparing functionalized derivatives, especially polyols (diols), polyamines, polyesters and epoxides, having commercially valuable properties without the need for expensive partial hydrogenation of the initial reactants.